What to do when Your Vehicle Check Engine Light Turns On and the Warranty has Expired

I wish to share this simple piece of information that has saved me thousands of dollars over the past several years.

Yesterday my vehicle check engine light turned on and I knew what to do.

I have never owned a new car; I always buy used. I usually buy an American model lease back or rental return with around 25,000 miles on it which saves me $10,000 – $20,000 on each vehicle purchase, and that allows me to stay out of debt (which my wife and I abhor). The risk is that the factory warranty expires 5,000 – 10,000 miles after purchase, so I could end up with a useless car less than a year after purchase, but that hasn’t happened.

What has happened is the check engine light frequently lights after the vehicle exceeds 50,000 miles. In the past when this happened, I always took the vehicle to a dealership to have them diagnose and fix the problem. I’d have to make inconvenient commuting arrangements since I’d loose the car for 1-2 days, and a repair was required that cost between $500-$2000 dollars. Since I am a mechanical know-nothing, I accepted the dealer’s word, made the repair, and paid the bill. I don’t recall how many times I’ve been through this repetitive cycle, but it’s been often enough to cause me a lot of frustration.

I don’t remember where I learned this, but several years ago, I learned that I didn’t need to go to a dealership or another garage to find out why the check engine light was lit. I didn’t even need to buy any special equipment to find out why it was lit.

Today I take the car to an auto parts store like Auto Zone or Advance Auto Parts and tell the guy at the counter that my check engine light is on. He plugs a handheld electronic device into my car, and tells me why it is lit. Several times, it said “emissions problem” – translated – A LOOSE GAS CAP! We tightened the gas cap, reset the light, and it didn’t light again for months. Other times it was a plug misfire, which can be a complete aberration. Again, we reset the light and it didn’t light again for months. A couple times, repairs were required, but at least I walked into the dealership with knowledge, which helped me keep the cost down. With knowledge of the problem, they couldn’t B.S. me.

The best part – it’s something you can do in five minutes that may save you thousands of dollars.

You can also buy yourself your own inexpensive Diagnositc Code Reader.

Check out Amazon’s entire assortment of ODBII Diagnotic Scanners.

To some readers this may be common knowledge, but for those of us that are mechanically challenged, it will save you cash.

170 thoughts on “What to do when Your Vehicle Check Engine Light Turns On and the Warranty has Expired”

  1. I have a 2005 Jeep Rubicon and the CEL came on after filling up with Exxon gas. Took to mechanic and tested it. Code 421(low efficiency bank 2 catalytic converter. He siad that the cat should be warrantied for 8yrs. or 80k miles through the factory. I have 27+k miles. Does anyone know the particulars on this?

  2. It is possible that you are using a lower octane of gas than what is recommended for your car. Possibly, the CEL is warning you to return to the higher octane. I don’t know about your warranty, but what I have heard is that, in general, catalytic converters do not malfunction, even in older cars (cars with over 100,000 miles). See if moving up to a higher octane makes the light go away. I would also suggest that you get an oil change done.

  3. I had the oil changed and added “Sea Foam additive” that my mechanic suggested the first the light came on about 3 fill-ups ago. The light came on again 2 days ago after fill-up. The manual calls for regular gas and have not had any trouble until recently with the CEL coming on. I am going to take it to the dealership where I bought it and have them check it and it is due for yearly inspection. If they do not warranty the cat I will have my son-in-law replace the converter for a whole lot less in cost. But if they do warranty it, we will be all the more better off, but cost wise and labor too. Thanks for your info.

  4. HI

  5. It seems to me that your gauge is electric, not a dipstick that goes directly into your gas-tank. IF that is the case, then, possibly, at the time of replacing your battery, the connection between the battery and the gaguge may have become loose or even intermittent, leading to a wrong reading on the gas-tank. This is just a guess but any decent mechanic should be able to tell in about 2 seconds if that is truly the case.

  6. I recently had the check engine light on my 95 Nissan 200 come on , infact it had become an on going thing . However this time the light remained on for several months . As the car was due for smog I knew I would have to fix this problem . I searched the web and took the advice of a consumer . I disconnected the positive lead of the battery ….waited about 10 mins and reconnected . The light remained on for the next trip of about 3 miles , however when I got back in the car to come home the light was off . I immediately drove to the smog station and it passed with flying colours !!!!!!!!
    Don’t let the garages rip you off , at least try this first..it worked for me !!!!

  7. I had a check engine light on.. and I did take it to Autozone and they said it would be my oxygen sensor. But I don’t know if something else is causing the oxygen sensor go bad, or should I get it diagonsed by a profressional

  8. In response to John and PJN,

    When using John’s instructions, my digital odometer give a numeric readout of the error codes..

    Thanks ALOT John!!

  9. I just checked with my local Auto Zone, and was told that they were not allowed to do the free CE check anymore.

    This might just apply to California as when I asked why, he said he thought there was some law that had been passed.

    I guess someone was losing money somewhere and they just had to mess it up for everyone else.


  10. Hi I have a 2001 Volkswagen Jetta with a 2.0 Engine. The check Engine light came on late last year….but after many tune ups, many mechanics found nothing wrong with the car. I got a reading from an Emissions Test that said my system was too lean….I’ve run an Octane Boost and am currently attempting to run a full tank of 93 Premium BP gas through my engine. The light is still on. Why needs to be done at this point. What has usually been the case for 2001 VW Jettas?

  11. I found out you can reset the check engine light by pulling out the efi fuse then replacing it !!! In my case though the light came back on so there must be something bad going on !! Might save you a couple of bucks if it was just your fuel cap !!

  12. I have been driving my daughter’s 2001 Jetta for the last 7 months. Like everyone else, all of a sudden the check engine light came on and I have had it looked at by a few places (other than the dealership) and they can’t find anything wrong. The problem is that now the car needs to be inspected and it won’t pass in NY with the light on… I wish just putting a piece of black tape over it would make it all better! LOL The guy actually did me a favor and reset it for me – rather than charging me, failing me and making me come back again anyway. He said to drive it for a while (I have till the end of November) and then come back and he will pass me as long as the light doesn’t come back on. It stayed out most of the day… but after I got the tank filled and turned it off, it came back on again later that day. I guess I am going to be forced to go to the dealership to get this taken care of… and while I agree with both sides about “dealerships” I can say that 2 tires that I could have gotten somewhere else for less than $100 bucks each ended up costing me over $300 total – but that is my own fault! ANY AND ALL SUGGESTIONS MUCH APPRECIATED!!!

  13. Since you asked for any and all suggestions, here are some that have worked:

    1. Turn your gas-tank cap until it clicks 3 times. If you don’t have a cap, buy one.
    2. Disconnect and reconnect your battery.
    3. Buy high-octane gas and fill your tank with it for 5 consecutive tanks.
    4. Replace all of your fuses.
    5. Get a tune-up.
    6. Add oil and/or get an oil-change.
    6. Change your air-filter.

    Basically, the light comes on for one of two reasons: A. There is a real problem with the engine. B. There is some type of minor malfunction that has something remotely to do with the engine. If you have a problem in category A, your car will stop driving in a day or two. In category B are electrical problems, fuel problems, and “safety” issues (such as the cap to the gas tank being loose or missing). Electrical problems can be caused by loose (or faulty) wiring/connections, a stuck switch, bad alternator, or bad battery. Fuel problems can be caused by someone maliciously dumping bad stuff into your fuel tank, buying fuel from an “ultra-cheap” gas station, buying low-octane fuel, bad fuel injection, and bad spark plugs. Safety issues include, mostly, being low on any or all fluids — engine oil, transmission fluid, power-steering fluid, engine coolant, etc.

    If you follow all of the 6 suggestions mentioned above, there is a pretty good chance that you will, most likely, eliminate the problem together. And if you don’t, you will almost surely pin-point the cause of it, without spending a fortune.

  14. This is the Loooongest list about Engine Light!!! My 2001 CLK320 started having the light coming on several months ago…I made about 6 or 7 trips to a repair shop…everytime, they used one of the possible causes as being the problem and about couple of thousands dollars later, I finally gave up and decided to replace the car. None of cleaning parts, replacing parts…Oxygen Sensor, Vaccum Leak, so and so worked. The light kept coming back aggrevating me.
    Guess what, the brand new 2008 MB C300 Sport that I bought back in June (only about 3000 miles on it) is having the same problems. In addition to the Engine Light issue, the window doesn’t shut correctly!!!

    I do have the OBD code reader and all that showed me was every single possible cause that there may be there and it doesn’t even clear the light…for some reason it thinks it’s erased the code, but the light is still shining!!!

    There is no straight answer to what the light is implying with or without code reader. Even the mechanics I’ve used couldn’t tell for sure. They just kept trying different options to see if any worked!!!

    So far I’ve read through LOTS of posts on all sorts of sites and none has given me a practical or easy solution. I just need to take it back in while there is warranty on it and have the dealer to check on it….I just HATE the inconvenience of taking it in…quite a PAIN and I wish at least they knew what the heck they were doing!!! At least 9 trips total (between the old car and the new) on the window issue and no resolution :-/


  16. i owned 1999 Honda LX and check engine light is on. i tried reading all of youre help and pls help me with this before i go to a shop and hopefully can do it myself. i have to drive my son to his doctors appointment regulary and really in tight budget. any of you guys advice me what to do thanks. BTW i bought my car used and have no idea of its history what a dumb nut! hehe.

  17. The advice of Comment #10 is absolutely valuable.

    The malfunction engine light is on for on my Camry 2003, mileage is 56000.
    I replaced gasket on fuel cap, light stays on.

    Today, after I cleaned the end of fuel hose and I pulled two fuses marked EFI for a few minutes, restarted the engine, the light went off.

    This avoid at least $60 diagnose fee per dealer.
    If the light is on again, I will go to Autozone to get the problem code, then go to the dealer.

  18. For CA drivers:

    Autozone no longer pull the code for you or let you borrow the scanner. You have to buy one. I was told that it is a new state regulation. I live in the SF Bay Area.

    I was battling with the CE light for over almost two years. Had it cleared, came back on, etc. Finally, I bought a scanner for $60, had the code pulled. It had something to do with low catelytic converter efficiency. Cleared the light. I changed the oil, air filter, checked all tire pressures, filled it up with premium gasoline. Drove for 200 miles and 40 cycles. Then drove 15 miles to the smog station. Passed smog, and light never came back on. Don’t know what did it.

  19. I tried the Fuse take out and put back technique as in POST 116, worked like charm. Will report if the check light comes back on.

    The Fuel cap trick had worked for a day, that the reason another try.

    CAMRY’97 LE 95k miles.

  20. The “SERVICE ENGINE SOON” light came on. I had the vehicle inspected at DMV approximately a week and a half ago where it passed everything including the gas cap inspection. I have now had multiple people tell me that about 1-2 weeks after having their vehicles inspected at DMV this same problem happened. After bringing my car to the dealership to see what the problem is and over $200.00 later, it is the gas cap. I am very upset over this and feel that whatever DMV does to vehicles for their gas cap inspection is causing this to happen which, in turn, is causing New Jersey vehicle owners to incur unnecessary expenses to repair something which is broken due to the NJ DMV Inspection Test. I am going to call the news stations and complain.

  21. I have been a technician for over thirty years and still doing it.I feel every one needs to learn about cars I learn every day.I have to speak my mine.Auto part stores are there to sale you parts and that’s what they do when you go there to get codes read.Let me explain a code will identify a problem in a sub system.It does not tell you what is wrong 90% of the time.If you have a code P0174 lean bank the guy at the parts store will sale you a 02 sensor but it could be a vacuum leak , dirty injector , dirty MAF. sensor a bad MAP. sensor etc. you see my point do not buy a lot of parts that’s what they want you to do. They can not diag. a car any better than you.Do not disconnect the battery It only works on about 2% of the cars what you do not know is it causes your computer to loose all of its programed memory this can cause more problems,cause a car not to start lose of emobilizer codes etc.almost all cars have it now..Never disconnect the positive side of battery this can cause a voltage spike that can kill your computer.Find a good/honest tech. ask if they are ASE certified the top technicians are ASE Masters and L1 ask for certs.Its your car.One more thing scanner companies are there to sale you scanners I’m sorry code pullers do you know what they mean save your money find a good technician. not a mechanic unless you need some maintenance done that brings up something else Honda service manual explains how to reset your maintenance light after you have a oil change not a check engine light be aware of free advice. A good scanner starts at about $6K and goes up I have over $13k invested in mine and over $100K in tools want to be a TECHNICIAN did not think so LOL. thank you got to go

  22. I think Ford is guilty of making those “snap on” fuel caps.

    You would not belief how much a “loose” or weaken fuel cap could affect the performance of a car.

    My car had had the “service engine soon” light on for serveral months. I thought it might not be due to the fuel cap, but I bought a replacement fuel cap at Walmart for $16.86 anyway. The replacement fuel cap is lockable so it can deter fuel stealing or sabotage of your fuel system.
    After putting on the new fuel cap and driving for about 1 mile, the “service engine soon” light was gone, and the car performed much better, without the “weak” feeling at low speed acceleration.
    The “snap on” fuel caps (like the one I have on my 1998 Mercury Sable) do not allow you to further tighten when the rubber ring on the cap is weakened or worn or “flattened” thus allowing vapor to leak.

    Note: when you first buy a lockable fuel cap, lubricate the key hole with WD40 or silicon spray, otherwise it could be difficult to unlock.

  23. You are smart to buy the vehicles that way. You can always buy an extended warranty, but I mean you’re never going to be totally out. If the motor goes or something, it will set you back a bit, but that would be very very rare. If you plan on doing any maintenance yourself the diagnosis readers are a good investment, but be careful who you tell or you will become a mechanic for all your friends lol.

  24. I had an issue with the ck engine light in my 2000 camry my mechanic told me to replace the gas cap reset the light and not to let the gas get real low in the car he told me a loose gas cap and letting your gas get very low will cause the light to come on. I Tested what he said to see if it is true it is. Now I know if I let the gas get to low the light will come on. Now I make sure I don’t let the gas get to low and I keep the gas cap tight and I have not had a problem since.

  25. Find a pro you know and trust, the dudes at Auto Zone and othger parts houses want to sell you parts. For example an o2 sensor code doesn’t mean replace the o2 sensor. I’ve seen computers replaced, when all it was was a fuse. Its hard to get good advise from some one who was selling french fries 2 weeks ago!

  26. Money available to clean air and improve smog program

    Charlie Peters, Clean Air Performance Professionals, March 22, 2010

    The Smog Check issue has been under continuous legislative debate since 1993. AB 2289 by Eng is an opportunity to improve program performance and public support.

    We at the Clean Air Performance Professionals propose “reasonably available control measures” to improve California Smog Check performance. Consider a Consumer Assistance Program (CAP) quality audit to improve smog check performance.

    We propose using the CAP cars and funds to provide a random quality audit (or secret shopper) of smog check providers. Audits that result in the car’s not being in compliance should be handled similarly to the former Consumer Repair and Education Workforce program. The Bureau of Automotive Repair program did not fine the licensees nor did it involve coercion. But when the question of “what would you like to do?” was asked, the shop took care of business and usually elected to fix the car.

    The average smog check failure repair is about $ 150.00 state wide. The motorist pays about the same at the average repair station and the CAP station. The average CAP repair is about $350.00. Many cars are not brought into compliance.

    To level the smog check failure repair playing field so more cars meet standards after repair, the whole smog check market should be subject to a CAP random audit.

    Around 1985, BAR started a “missing part” audit. In 1991 that program was stopped, The difference was a 300 percent change in result in finding the missing part.

    When BAR ran less than one audit per station per year, the result was a change in behavior that started at more than an 80 percent rate, but moved to less than 20 percent rate of noncompliance.

    The difference was a 300 percent change in result in finding the missing part. If the CAP audit was addressing the issue of repair compliance rather than just finding a missing part, the results may be the same or a 300 percent improvement in compliance. With the missing part program, a follow-up audit with increasing demands lift the stations no options but to find the missing part or be removed from the game.

    There are huge inconsistencies from Smog Check station to station and with BAR representatives. For BAR to decide a car is not in compliance, rules of Smog Check must be clarified. Money is available for the CAP program. It can be used for contracted scrap and repairs, or some of the funds can be used to evaluate and support improved performance of licensed small business. The cars and funds are the same, but the results may be credit for 2,000 tons per day in pollution prevention credit in the State Implementation Plan, rather than our current credit of fewer than 400 tons per day.

    The governor and state Legislature would get the credit for improved performance. Performance improvements would be accomplished at a cost of less than $500.00 per ton. And program illusions would be reduced in 1 year.

    Charlie Peters is president of Clean Air Performance Professionals.

    CAPP contact: Charlie Peters (510) 537-1796 cappcharlie@earthlink.net

  27. I just came from auto zone and they said they can no longer hook up there computer to you car because they are not certified to diagnose it….. now im stuck!

  28. California Smog Check providers fail millions of cars but Chief Sherry Mehl, DCA/BAR, has never found out if what is broken on a Smog Check failed car gets fixed. 510.537.1796

  29. it is not legal for a parts store in California to use the electronic reader on your car unless they have a maintenance shop, try Pepboys, they did not charge me to do it yesterday, but the autozones and kraigens told me they were not allow to

  30. Have a 2001 ToyotaCamry Le, ce light on and off, replacing parts costing me arm and leg still no cure, Trying to get inspection sticker and it will not pass so give up. please send your remedies

  31. I Have a Toyota Spriter from 1994. a few weeks ago I had problems with over heating and i bougth a new radiator. afterwords the mech told me that it was the wather pump that was leaking, and we end up replacing the water pump. but at this time e so that a small tube was broken and replace it as well.
    from that day when i’m in ascending position or I have to make a rough start our rough aceleration my car lites the check engine and looses power.
    My mech told me that is has nothing to do with the water pump change and I should take the car back to reset the ligth and the matter would be solved.
    What can I do.

  32. Hey,

    Thank you so much for this information. I just had a check enigine light lit up and i learned from my last time repair that knowing what exactly is the problem with your car before you go to a repair shop is a good money saving thing to do. My Ac wasnt working prices i got from repair shop were 600 & 700 to fix it one of my A/C refrigerant pipe was leaking and everyone wanted more than $200 for the pipe i got the pipe from online for $40 and got everything done for $240.
    Just wanted to share. thank you for your information. Take care.

  33. Can anyone help me. In my chevy trailblazer 2004 The Anti-lock Brake System (ABS) light comes on. The the transmission goes into limp in mode. Does anyone knew what the problem could be an how to fix it?????

  34. I have an 04 Honda Pilot. The check engine light went on and
    among many opinions, was to get a new gas cap. No help at all until I lubricated the rubber ring in the gas cap with light engine oil or even something like vaseline would work. The engine light went off immediately. Who knew?

  35. Continuation of Post 120. 2002 Corolla, slightly over 100K miles. Two years later, it is smog time again. don’t you know it, the Damn CE light came on again. Code 420 – catalyst low efficiency (bank 1). Dealer said it is likely the catalytic converter. labor: 150. Part: $1300+.

    I blurtly out laughing when I heard the quot because it is so outrages – like highway robbery. The car runs absolutely fine. It gives me good gas mileage, etc. I have to pay $1500 just to have this car pass the stupid smog test? And what if I had the Cat replaced and it still pass smog???

    Thanks for the tips on post 127 and 140. I may not have made sure that the gas cap is tight enough and I have a habit of letting the gas run really low before filling up – although last time the light came on right after I fill up (gas cap not tight enough, may be).

    My car also burns oil and before you know it, it is so low that I had to add one gallon of oil. But the light came back on after I added the oil anyhow.

    Now, the oil and gas are full. Tighten the gas cap. Cleared the light. Drove 36 miles, no light yet. Waiting and see. may be replace the air filter or get a tune up.

  36. Most codes are small and come from something as small as your gas lid not being on tight enough. You can do the battery trick to see if it gets rid of the code by disconnecting your negative cable but its better to just to go to a local shop or part store they well look up the code for free and can tell you exactly what it is. If small thing they can just delete it for you also.

  37. i have a 200 camry with check engine light on,repaled fuel cap,replaced vps switch,replacec vacuum modulater,cleaned intake,replaced,coolent sensor,both co2 sensers,replaced vacuum lines.
    Answer this one i still have acode p401 pops up check engine back on again after twenty five miles.
    Please help!

  38. continuation of 141. I cleared the code PO420 with the scanner I bought. Drove 50 miles. Had it smogged. Passed. Obviously, ther is nothing wrong with the CAT or it would not have passed smog.

    Then around 100 miles after I cleared the code, it came back on. Cleared it. Drove it, came back on. The cycle repeats itself anywhere between 45 to 75 miles after I cleared the code.

    Now, I don’t even bother to check or clear the code any more. Since it passed smog. I am good for another 2 years.

    Will leaving the check engine light (Code PO420, Catalyst efficiency low, bank one) on cause any problems?

  39. RE: Check engine lights. It may be a random warning that resets itself or one that needs to be reset with one of the many methods listed on this site. It can be a great indicator of what the problem is that is, EX. when an engine is missfiring, it will tell you lots of good info if you have the “reader”. Cosco has one for $39 and it tells you the codes and a short description of what the error is and it will erase the error code.
    These testors may cost you anywhere from $39 (Cosco) up to $200 or more.
    Good luck.

  40. In NH you cannot just disconnect the battery for a few minutes to turn the light off, then run to get your inspection sticker.
    Every year you have to have an inspection, and the mechanic has to plug into the OBD system. If the light has been reset, a code comes up indicating so! You must drive 50 miles after a reset, so the light can come back on. You can’t fool the system by a reset, or putting tape over the light, or pulling out the fuse. And let me tell you it sucks because an exhaust leak 1/1,000/000th of a molecule will trigger the light, and you will spend $100s if not $1000s trying to fix it. Every year. I think its a big scam between mechanics and the state to get your money!

  41. Off topic but goes to the millions of dollars wasted by everyone:

    The total square miles of populated areas where car density is high is only 3% of the earths square miles. If these friggin moron tree huggers think all the money we’re spending on pollution prevention is going to improve or make any difference in the air quality of the planet, they are smoking something funny! Look at other countries like China, India, etc. No pollution control and they are doing fine!

    All the cubic feet of exhaust emissions per day compared to the total volume of air on the planet would amount to a cup of water in the oceans! Why do people think they have any effect on the planet? This goes to the idiots who think humans are causing global warming. They ignore the scientific facts substantiated through real research that the earth goes through a cycle of warming and cooling roughly every 10,000 year intervals. We are coming out of the cooling period and heading towards the warming part of the cycle. What could they blame the slight warming trend in the 1800’s on when cars were not around? Cow and horse farts?

    Just my 2 cents.

    BTW, I cleared my CEL 10 min before smog check in CA last month. Next day it came back but got my certificate that my car passed. Screw the state of CA!

  42. I have a HONDA ACCORD 2.4 2005, and the CEL came on a few days back. Sometimes it’s on and sometimes it doesn’t. When the engine is cold (in the morning), it’s mostly on. Sometimes after restarting the engine, it’s off. It’s normally off in the afternoon.

    Can I assume this is something not serious yet, and shall I visit the local mechanic even when the CEL is off?

  43. The guys at the auto parts store erased the history, but i need to take the car to a mechanic for a diagnosis of the emissions problem.

    About how long until the light comes back again….so the mechanic can hook up my car and get a true diagnosis of the problem?

  44. I bought a new car once and will never do it again. My eyes are very open to the savings you get by buying an older model. Even a model from 2+ years ago can save you thousands. Needless to say, my $15,000 car that I bought in 2002 cost me $20,000 (w/interest) and is now worth $2500. Definitely buy used! It’s really not that much of a compromise.

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